The present invention relates to drug delivery systems, particularly to implantable drug delivery systems, and more particularly to an implantable, microfabricated, fully integrated drug delivery system capable of secreting controlled dosages of multiple or single drugs over long periods of time.
Historically, pharmaceutically active agents have been chosen based on biological activity, with absorption, efficacy, and side effect profiles determined by metabolic process. The effectiveness of the therapeutic agent can be enhanced by sophisticated drug delivery systems that actively control the delivery rate and site of drug action.
Alza Corporation, Palo Alto, Calif., has developed a drug delivery system that uses osmotic pressure to infuse drugs, as exemplified by U.S. Pat. No. 5,151,093 issue Sep. 29, 1992. Also Alza Corporation has developed an implantable drug delivery system using osmotic pressure which basically consists of a titanium tube having a water-permeable membrane on one end, and containing a salt pellet, piston, and drug, with an orifice on the opposite end. Water diffuses through the membrane and creates a high concentration NaCl solution by dissolving the salt pellet. Additional water is driven into the device due to the concentration gradient across the membrane, generating osmotic pressures as great as 3000 psi. The pressure pushes on the piston and forces the drug through the orifice at a constant rate. The implantation is performed using a trocar (large syringe) by a physician, after which drug delivery is automatic, eliminating the rests of patients forgetting to take prescribed medication. For infections diseases such as hepatitis, implants such as these will avoid the creation of drug-resistant strains by patients who neglect to complete their prescribed drug schedule. In addition these systems will aid individuals in long-term health management such as hormone therapy.
The prior implantable systems can be improved considerably by reducing the size and adding flow control to enable variable and programmable dosage profiles. This invention allows for delivery of multiple drugs over a period of time and can be programmed or externally controlled. And can be powered by a number of means: 1.) Osmosis; 2.) Thermopneumatic; 3.) Thermal bimorphs; 4.)Shape memory films; 5.) Piezoelectric bimorphs. The drug delivery system having multiple channels to allow for controlled delivery profiles, precise drug metering, and the ability to independently control delivery of several drugs or drug combinations with the same device. The miniature device of the present invention can be implanted prophylactically and lie dormant until activated in response to a therapeutic need by an externally located controller via implanted electronics. Thus, the present invention enables the administering of any drug (vaccines, booster, hormones, antibiotics, etc.) at either discrete time intervals or at a specified rate, such as to soldiers in a controlled manner or in response to a chemical/biological warfare attack.
It is an object of the present invention to provide a microfabricated in injectable drug delivery system.
a further object of the invention is to provide an implantable drug delivery system which may be controlled externally.
a further object of the invention is to provide an implantable, osmotic engine-based drug delivery system, which utilizes polymer pistons for isolating the pressure source from drug-filled microchannels.
Another object of the invention is to provide a micromachined implantable, osmotically driven drug delivery system utilizing shape memory polymer valves for controlling the osmotic engine and drug outlet ports.
Another object of the invention is to provide an implantable drug delivery device which includes an anisotropically-etched, atomically-sharp silicon leading edge for penetrating the skin during implantation.
Another object of the invention is to provide a drug delivery device of a stacked modular disc-shaped design incorporating membranes for displacing the drugs.
Another object of the invention is to provide a pumping and valving arrangement that could also be used to deliver samples, reagents, and other fluids in ex-vivo microfluidic-based medical diagnostic instruments.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. Basically the invention involves a microfabricated injectable drug delivery system which includes an inplantable, osmotically driven device controlled by shape memory polymer valves which can be activated by an external controller. The implantable osmotic driven device utilizes microfabricated polymer pistons for isolating the pressure source from drug-filled microchannel (an equivalent to microscale syringes). The implantable device is scalable to accommodate a broad range of desired drugs and/or drug volumes. Potential applications for the invention include response to detection of biological or chemical warfare threats, regulated delivery of vaccines or boosters (e.g. anthraxxe2x80x949 boosters over 18 mos.), hormone therapy, onxe2x80x94demand pain medication and insulin delivery for diabetes management. A demonstration embodiment of a silicon and glass-based device includes an array of four parallel osmotic pumps fabricated on a single 4 mmxc3x971 mmxc3x9725 mm member.